The Milky Way nuclear star cluster beyond 1 pc

Within the central 10 pc of our Galaxy lies a dense cluster of stars, the nuclear star cluster, forming a distinct component of our Galaxy. Nuclear star clusters are common objects and are detected in ~75% of nearby galaxies. It is, however, not fully understood how nuclear clusters form. Because the Milky Way nuclear star cluster is at a distance of only 8 kpc, we can spatially resolve its stellar populations and kinematics much better than in external galaxies. This makes the Milky Way nuclear star cluster a reference object for understanding the structure and assembly history of all nuclear star clusters. We have obtained an unparalleled data set using the near-infrared long-slit spectrograph ISAAC (VLT) in a novel drift-scan technique to construct an integral-field spectroscopic map of the central ~10 × 8 pc of our Galaxy. To complement our data set we also observed fields out to a distance of ~19 pc along the Galactic plane to disentangle the influence of the nuclear stellar disk. From this data set we extract a stellar kinematic map using the CO bandheads and an emission line kinematic map using H2 emission lines. Using the stellar kinematics, we set up a kinematic model for the Milky Way nuclear star cluster to derive its mass and constrain the central Galactic potential. Because the black hole mass in the Milky Way is precisely known, this kinematic data set will also serve as a benchmark for testing black hole mass modeling techniques used in external galaxies. Copyright © International Astronomical Union 2014.